With the development of micro- and nanotechnology, there is increasing demand for measurement of the surface shape of a fine structure.
Surface shape measurement methods may be divided into contact and non-contact measurement methods based on the type of measurement. Thereamong, the non-contact measurement method is an optical measurement method using light, and causes less physical damage to a specimen while allowing faster measurement than the contact measurement method and thus is widely used throughout the industry.
Various types of microscopes have been developed to realize such ultrahigh resolution imaging. In particular, some microscopes adopt a method of maximizing the number of distinguishable image pixels by increasing the resolution of an image sensor, such as CCD/CMOS, a method of minimizing chromatic aberration generated by a lens such as an aspherical lens, and a method of increasing resolution by correcting an image acquired by an image sensor through digital processing.
Recently, there has been proposed a composite 3D image acquisition apparatus that acquires plural images and performs digital post-processing of the plural images. Examples of a method employed by such an image acquisition apparatus may include a high dynamic range (HDR) technique that acquires plural images under different exposures, followed by digital post-processing to improve optical depth, a structured illumination modulation (SIM) technique that acquires multiple pattern images having different phase contrasts by imparting a predetermined pattern to light incident on a measurement object, followed by comparison between the pattern images to improve resolution.
What the HDR technique and the SIM technique have in common is that plural images having certain characteristics imparted thereto are first acquired and then a single image having improved resolution is acquired through digital processing. However, the HDR technique has a problem in that it takes a relatively long time to acquire plural mages, and the SIM technique has problems of high cost and low image processing speed due to sequential acquisition of plural images despite the advantage of allowing acquisition of a high-resolution 3D image.